Conventional thread sewing machines can only ever be set up for one format. This takes place by means of mechanical connections, for example by the use of multi-tooth couplings and magnetic brakes, during the setting up of production. In the course of production itself, this system cannot be adjusted, or is at least not flexible enough. This leads to problems when book blocks are to consist of signatures, also called printed sheets, of different sheet lengths, for example when, as an art print, or for design reasons, they have different formats.
In particular when printed sheets are transported on the foot side and are scanned on the head side or transported on the head side and are then to be transferred from one transport section to another, because of the inflexible format adjustment due to the machines this is not possible or only with restrictions, this regularly entailing a reduction in the production speed, a machine stoppage or the constant placing of the printed sheets by hand.
When printed sheets of various sizes are directly placed by hand on a sewing saddle, as is currently practised, dangerous safety-related sequences that are no longer permitted by the safety authorities are produced as there is thus an imminent great danger for the user of the machine of serious finger injuries.
Purely for safety-related reasons, machines with an auxiliary saddle support would therefore be preferable. The drawback in these machines is the constantly recurring monotonous movement sequence of the operator when placing the individual printed sheets opened by hand. Moreover, the risk, which is not to be underestimated, exists here of the printed sheets being able to become mixed up, which can lead to a not inconsiderable rejection rate. Nevertheless, the fact is, that a manual placing of printed sheets with different formats on the auxiliary saddle is only possible when the entrainer chain does not have a fixed position.
Another possibility for producing a book of this type with sub-format insertions is to divide this book into a plurality of parts and to then bring them together sewn by thread. In a process of this type, all the fully printed sheets, which are also called standard-format printed sheets, are firstly sewn as far as a sub-format printed sheet. All the following standard-format signatures are thereupon processed and, finally, the sub-format printed sheets are sewn. Lastly, a book is then produced with at least three thread-sewn, part-book blocks, which can be glued together in the correct order.
As the demand for books of this type, in which sub-format printed sheets are incorporated for design reasons, is increasing, the sequences that have become known in the prior art in conjunction with thread sewing machines are no longer satisfactory as, as in all the techniques that have become known, it is not possible to realise economical, safe production.
In this context and with regard to the prior art that has become known, reference is made in a subsidiary manner to the document EP 2 184 177 A1 which describes a device for thread sewing folded print products. In this case, the individual printed products are sewn by a sewing machine at their fold and sewn together to form a book block at their back having the fold, the printed products being fed in a pivotable saddle, which they individually rest astride, to the sewing station. EP 2 184 277 A1 is hereby incorporated by reference herein in its entirety.
EP 1 561 599 A1 deals with the exact and flexible positioning of standard-format, folded printed sheets on a sewing saddle, which are retrospectively bound, i.e. thread-sewn, to form a book block. The thread sewing machine inter alia has a feeder as well as a downstream sewing saddle. The printed sheets are taken over from the feeder by means of a conveying mechanism of the sewing saddle and transported into a sewing position on the sewing saddle. For this purpose, the conveying mechanism has a drive connection to a rotation-angle controlled electric motor configured by a computer-linked controller. The computer has a data memory, in which data corresponding to the format of different printed sheets are stored, whereby the conveying mechanism can easily be adjusted or converted to the specific format size of the printed sheets to be processed. In addition, a stop corresponding to the sewing position of the printed sheets and determining the end position of a printed sheet can be arranged on the sewing saddle, said stop being used to orient the front edge of the respective printed sheet. As an alternative or in addition, a sensor determining the end position of a printed sheet and oriented to the sewing saddle may also be allocated to the sewing position. All the variants of this solution are, however, merely oriented to the exact and flexible positioning of standard-format printed sheets, so this solution does not make any contribution to the production of book blocks consisting both of standard-format and sub-format printed sheets.